This application relates to liquid holding tanks having one or more relatively thin, planar side walls. More particularly, this invention relates to liquid holding tanks made of thin and flexible materials, the shapes of such tanks being reminiscent of rectangular parallelepipeds.
As used herein, a parallelepiped is considered to be a volume or body bounded by four rectangles and two parallelograms. A rectangular parallelepiped, however, is a parallelepiped, all six faces of which are rectangles or substantially rectangular. A rectangular parallelepiped is also considered to be a right prism, the bases of which (top and bottom surfaces) are parallelograms. A cube is a rectangular parallelepiped because it is a volume or body bounded by six identical squares, the squares being rectangles.
A problem with holding tanks having thin, flat side walls is that such walls tend to bow outwardly when the tank contains liquid because of the distributed force exerted on the walls by the liquid. As the level of the liquid in the tanks rises, the outward deflection of the walls increases. Outward deflection of sidewalls used in a rectangular, parallelepiped-shaped tank can make it difficult to remove the tank from a space wherein the nominal tank width is such that it just fits into the space.
The inward deflection of a tank's sidewalls can also be problematic. In many liquid holding tanks, the level of the upper surface of the liquid held in the tank is used to determine the volume held in the tank. The height of the upper level also determines the pressure at the bottom of the tank. Since most liquid dispensers draw liquid from the bottom of the tank, the height of the upper level will determine not only the flow rate from the tank but also the apparent volume left in a tank. A liquid holding tank with thin walls that are able to be held upright would be an improvement over the prior art.